Vehicle gas turbines with ratio couplings therebetween-therefor

ABSTRACT

Gas turbine unit for motor vehicles in which the compressor turbine is selectively connected to the output shaft through a controllable fluid coupling so as to provide a transfer of power to the output shaft from the compressor turbine during partialload operation and a transfer of power from the output shaft to the compressor turbine during braking.

United States Patent [191 Mi iller et al.

[ Mai. 19, 1974 VEHICLE GAS TURBINES WITH RATIO COUPLINGSTHEREBETWEEN-THEREFOR [75] Inventors: Dieter Miiller, Stuttgart; WilhelmJurisch, Nellingen Kr. Esslingen, both of Germany [73] Assignee:Daimler-Benz Aktiengesellschaft,

Stuttgart-Unterturkheim, Germany [22] Filed: Apr. 5, 1973 [21] Appl.No.: 348,079

Related US. Application Data [62 Division of Ser. No. 121,956, March 8,1971, Pat.

[30] Foreign Application Priority Data Mar. :6', 1970 Germany 2010581[52] US. Cl. 60/39-16 R, 74/DIG. 5, 74/661 [51] Int. Cl. F02c 3/10 [58]Field ofYSearch 60/3916, 39.14; I 74/DIG. 5, 661

[56] References Cited UNITED STATES PATENTS 3,546,879 12/1970 Hass60/3916 R 3,626,692 12/1971 Kumm 60/3916 R 3,313,104 4/1967 Evans etaL... 60/3916 R 3,488,947 1/1970 Miller et a1. .1 60/3916 R 3,237,4043/1966 Flanigan et a1. 60/39.16 R 3,266,248 8/1966 Leslie 60/3916 R3,635,019 1/1972 Kronogard et a1. 60/39.]6 R

Primary Examiner-Carlton R. Croyle Assistant ExaminerWarren OlsenAttorney, Agent, or Firm-Craig and Antonelli [5 7] ABSTRACT Gas turbineunit for motor vehicles in which the compressor turbine is selectivelyconnected to the output shaft through a controllable fluid coupling soas to provide a transfer of power to the output shaft from thecompressor turbine during partial-load operation and a transfer of powerfrom the output shaft to the compressor turbine during braking.

7 Claims, 4 Drawing Figures VEHICLE GAS T URBINES WITH RATIO COUPLINGSTHEREBETWEEN-THEREFOR This is a division of application Ser. 'No.121,956 filed Mar. 8, 1971, now US. Pat. No. 3,744,241.

The invention relates to a gas turbine unit for driving vehicles,especially motor vehicles, including a compressor, a compressor turbineand a power output turbine.

Usually such units are constructed in such a way that the compressorturbine mounted on the same shaft as the compressor serves exclusivelyfor producing power for the compressor; whereas, the power for drivingis derived exclusively from the power output turbine. The invention hasthe objective to improve the partial-load behavior of such gas turbineunits and to make engine braking possible.

The invention consists therein, that the compressor turbine isclutchable, i.e., selectively connectable, with the power output shaftdriven by the power output turbine. By this means, the specific fuelconsumption during partial-load operation can be improved because then apart of the compressor turbine output can be transmitted to the poweroutput shaft. Furthermore, an engine braking effect is obtained therebysince, through the connected compressor turbine, the compressor can pickup power and can thus absorb it.

In order to ensure that the transfer of energy is not only effective atreduced traveling speed and in order to obtain a constant brake actionthroughout a certain range, a speed reduction device can be provided inan especially favorable way between the compressor turbine and the poweroutput shaft, which can be controlled for engine braking and regulatedto a negative value and, for partial load driving, to a positive differ!ence in rotating speed in relation to the power output turbine. By thismeans, it is assured, that power can be transferred from the compressorturbine to the power output shaft at all vehicle speeds; whereas, duringengine braking, the braking effect is increased so that by thecontrollable difference in rotating speed, the compressor can be held ata high rotating speed, whereby its output for receiving energy may befully utilized through a certain time span.

A favorable embodiment of the invention is obtained when, in the gearreduction between the power output turbine and the output shaft, acoupling half of a controllable fluid coupling is arranged, the othercoupling halves of which being connected through a two-step controllablespeed reduction mechanism with the compressor turbine. Throughcontrolled filling of the fluid coupling and through change-over of thespeed reduction mechanism, selection can be made as to whether theenergy of the compressor turbine should be utilized for increasing thepower of the output turbine or whether an increased engine brakingeffect should be attained. Appropriately, for the change-over of thespeed reduction and for filling of the fluid coupling, a brake lever orthe like and a partial-load regulator may be provided.

A structurally favorable embodiment of the invention is obtained whenthe speed reduction mechanism consists of a planetary gear, the outerrim of which is braked for partial-load driving; whereas, it isconnected for engine braking through a freewheeling arrangement directlywith one of the coupling halves. By this means the desired differencesin rotating speed may be developed in a simple manner.

In the other embodiment of the invention the power output turbine maydrive, aside from the power takeoff shaft, two coupling halves of twocontrollable fluid couplings with different speed reductions, theassigned coupling halves of which are connected to the compressorturbine. By the selection as to which of the fluid couplings is to beput into operation, the desired positive or negative differences inrotating speed can be obtained with this embodiment without therequirement of switching to a mechanical speed reduction gear.

In a favorable manner, the coupling halves, driven by the compressorturbine, may be connected with each other to form with the assignedcoupling halves, driven by the power output turbine, a double fluidcoupling. Appropriately, for the control of the fluid couplings a brakelever or the like and a partial-load regulator are provided whichcontrol the degree of filling of the fluid couplings.

ln order to ensure, with both structural arrangements, that thecompressor turbine and the compressor are not subject to overspeed, itis especially advantageous when the fill quantity of the fluid coupling,during engine braking, is regulatable through a rotative speed limiterconnected to the power output turbine.

It is an object of the present invention to improve the partial-loadbehavior of gas turbine units for vehicles.

It is another object of the present invention to improve the fuelcomsumption'during partial-load operation of a gas turbine unit forvehicles.

It is a further object of the present invention to achieve an enginebraking effect in a gas turbine unit for vehicles.

It is still another object of the present invention to ensure aneffective transfer of energy at reduced speeds between the compressorturbine and the output shaft in a gas turbine unit by means of aclutchable coupling thereb etween.

It is still a furtherobject of the present invention to provide for thetransfer of power selectively in either direction between the compressorturbine and the output shaft of a gas turbine unit.

It is another object of the present invention to ensure that thecompressor and compressor turbine of a gas turbine unit are not subjectto overspeed.

These and other objects, features and advantages of the presentinvention will be more apparent from the following detailed descriptionwhen taken in conjunction with the accompanying drawings, wherein:

FIG. l shows a schematic diagram'of one embodiment of a gas turbine unitin accordance with this invention;

FIG. 2 is a schematic diagram of another embodiment of the invention;

FIG. 3 is a diagram illustrating the transmittable power for a gasturbine unit, according to FIGS. 1 and 2; and g FIG. 4 is a diagramillustrating the attainable engine braking effect for a gas turbine unitaccording to FIGS. 1 and 2.

The gas turbine unit shown in FIG. 1 essentially consists of acompressor 1 which, together with its compressor turbine 2 is mounted ona common shaft 3, and

a work or poweroutput turbine 4 which-is connected to the output shaft 6through a reduction gear 5. The gas is received by the compressor 1 at apressure temperature P T and is compressed to P T Passing through a heatexchanger 7, it is brought to the pressure-temperature condition P T andfrom there it is passed to a combustion chamber 8 in which it is broughtto the pressure-temperature condition P T In this condition it is fed tothe compressor turbine 2 where it expands to the pressure-temperaturecondition P T By this means, the required power for the compressor l isproduced. Thereafter, the gas is fed to the output turbine 4 in which itexpands to the pressuretemperature condition P T by giving up power(work). After this, it is discharged through the heat exchanger 7 to theatmosphere.

Usually with gas turbine units for vehicles, the rotary speed of thecompressor 1 and the compressor turbine 2 as well as the output turbineis very high. For example, the compressor 1 and the compressor turbine 4may be as high as 70,000 RPM, whereas the output turbine 4 may thenrotate at about 50,000 RPM. The high rotating speed of the outputturbine 4 usually has to be reduced at the output shaft 6. This isaccomplished through a reduction gear mechanism 5.

In order to make it possible that the power of the compressor turbine 2as well as the power of the output turbine 4 can be utilized, and toalso obtain an engine brake effect, in accordance with the presentinvention the compressor turbine 2 is clutchably connectable with theoutput shaft 6. This is accomplished through a controllable fluidcoupling 9, one half 10 of which is connected with the reduction gear 5between the output turbine 4 and output shaft 6 and the other half 11thereof is connected to the compressor or turbine 2 through a two-stepreduction on mechanism 12. For this purpose, the shaft 3 of thecompressor turbine 2 and the compressor 1 is extended and is connectedwith the clutch half 11 through a planetary gear. Step 14 of theplanetary gear is driven by the shaft 3 of the compressor turbine via agear 13, the outer rim 15 of which is held stationary by means of a bandbrake 16 and the inner rim 17 thereof is connected with clutch half 11.When the band brake 16 is released, the outer gear 15 is connected withthe clutch half 11 through a freewheeling arrangement 18. Between thecompressor turbine 2 and the coupling half 11, a two-step gear reduction12 is provided which is selectively controlled in such a manner that thecoupling half 11 connected to the compressor turbine 2 via the shaft 3produces a positive or negative difference in rotative speed in relationto the coupling half 10 firmly connected to the output turbine 4.Depending on which operating requirements are desired, the gearreduction is operated and the fluid coupling 9 is filled. Forpartial-load driving, the band brake 16 is held closed so that the outergear 15 of the planetary gear is held stationary and the coupling half11 shows a positive difference in rotating speed in relation to theother coupling half 10. For engine braking, the band brake is releasedso that the coupling half 11 receives a negative difference in speed ofrotation relative to the other clutch half through the outer gear 15 ofthe planetary gear and the freewheeling arrangement 18.

Filling of the fluid coupling 9 and the engaging and disengaging of theband brake 16 is accomplished at one time by means of a brake lever 19or the like, which operates a servo-piston 20 which, on the one hand,acts on the hand brake 16 through a power piston 21, and on the otherhand, controls the filling of the fluid coupling 9.

During partial-load driving, oil is supplied by an oil pump22 through apartial-load coupling regulator 23 of the fluid coupling 9 so that thecompressor turbine 2 tramsmits power to the power output shaft 6 througha speed reduction 12.

For engine braking, oil from the oil pump 22 is supplied to the fluidcoupling 9 through the servo-piston 20 whereas, at the same time, theband brake 16 is released so that the compressor 1, the compressorturbine 2 and the assigned speed reduction 12 may receive power.

In order to avoid overspeeding of the compressor 1 and compressorturbine 2 during engine braking, a revolution limiter 24 is providedwhich is connected through speed reduction steps 25 with shaft 3 of thecompressor 1 and the compressor turbine 2. This rotating speed limiter24 is arranged in the hydraulic regulating device in such a manner, thatit reduces the fill quantity of the fluid coupling 9 supplied from theservo-piston 20 during engine braking corresponding to the requiredneed.

The gas turbine unit according to FIG. 2 corresponds entirely in itsthermodynamic arrangement with that of the gas turbine unit according toFIG. 1. The output turbine 4 drives the output shaft 6 through a gearreduction 26. In order to also provide a possibility here to clutch theoutput shaft 6 with the compressor turbine 2, a double fluid coupling 27is provided. The two outer coupling halves 28 and 29 of the double fluidcoupling 27 are built into the speed. reduction 26 between outputturbine 4 and output shaft 6 so that it may be driven from the outputturbine 4 with different speeds of rotation. The two inner couplinghalves 30 and 31 are fixedly connected with each other and are driventhrough a gear step 32 directly from shaft 3 extending beyond thecompressor turbine 2 of the compressor 1 and compressor or turbine 2.The drive of the outer coupling halves 28 and 29 of the double fluidcoupling 27 is accomplished in such a manner, that, in one of theembodiments, the right coupling half 29 shows a positive difference inrotating speed relative to the two inner coupling halves 30 and 31,whereas the left coupling half 28 receives a negative difference inrotating speed.

For partial-load driving, oil is supplied to the fluid coupling 29,31,shown to the right in the drawing, from an oil pump 32 throughpartial-load coupling regulator 33, which regulates in the same manneras the regulator 23 in the embodiment according to FIG. 1, the quantityof filling being regulated in dependence on the rotating speed of thecompressor and the temperature in the combustion chamber. In thiscontrol position, the compressor turbine 2 may now transmit power to theoutput shaft 6.

For the engine braking process, a servo-piston 35 is operated through abrake lever 34 or the like which opens a connection between the oil pump32 and the left fluid coupling 28, 30. By this means, the compressorturbine and also the compressor are connected with the output shaft.However, a negative difference of speed of rotation is obtained,controllable by the filling quantity, so that the compressor 1 mustabsorb power. Also in this embodiment of the invention, a speed limiter36 is connected with the shaft of the compressor turbine which, in orderto avoid overspeeding of the compressor 1 and compressor turbine 2,reduces the quantity of fluid allowed to flow through the servopiston 35to an acceptable value.

In both embodiments, the fluid couplings 9, 28, 30, 29 and 31 which areused empty themselves automatically when the supply of oil thereto isstopped.

FIG. 3 shows how, as in the gas turbine units according to FIGS. 1 or 2,it is possible to utilize power during partial-load driving independence on the driving speed. Above the speed of driving V inpercent, which is subdivided into four steps, the speeds of rotation(rpm) n1 and n4 of the compressor 1 and the output turbine 4 are plottedalso in percent. Furthermore, the net outputs P at various partial-loadranges are shown in the area of the fourth step. Among the variouspartial-load curves, the solid line shows which portion of the net powerthe compressor turbine 2 can take over when the compressor turbine 2 isconnected with the output shaft 6 and the output turbine 4 at equalrotating speeds. The dashed lines show which share distribution ispossible when a positive difference in rotating speed at the fluidcoupling 9 or 29, 31 between the compressor turbine 2 and the outputturbine 4 exists. The cross-hatched portion of the diagram reveals thatit is only possible when the output turbine and the compressor turbineare connected with the output shaft at the'same speed, to transmit powerfrom the compressor turbine to the output shaft at reduced speed oftravel V. In contradistinction, the slanted shaded area reveals thatwith a positive difference of rotation, also at high speed of travel Vand partial-load driving, power can be transmitted from the compressorturbine 2 without difficulty.

In FIG. 4, the brake energy PB of the compressor l in percent is plottedabove the speed of travel V also in percent subdivided by steps. Thesolid curve 37 shows the energy the compressor can absorb for the casewhere the output shaft is connected to the com pressor turbine at anequal rotating speed. It shows clearly that the brake energy PB dropsoff rapidly with the speed of travel so that a favorable braking canonly be attained through a very small range of the speed of travel. Thedashed curve 38 shows that the brake energy PB of the compressor may beraised considerably when a difference in rotating speed between theoutput shaft 6 and the compressor turbine 2 can be maintained whereby,through the regulation of the filling of the fluid coupling 9 or 28, 30,the maximal rotating speed of the compressor 1 may be maintainedthroughout a larger range in, which its maximum power as engine brakingenergy PB can be reached. In this range, the braking energy PB of thecompressor 1 amounts to close to 100 percent. The droppingoff of thebraking energy then takes place at considerably lower speeds of travel.In this case one has to shift into the next lower gear. The portionextending from the dashed curve 38 is based on the effect of therotating speed limiter 24 or 36 which avoids overspeeding of thecompressor 1. The difference in rotating speed in both directions isselected so that it amounts to 30 percent; whereby, during enginebraking, the brake energy PB remains about constant over one stepwidths.

While we have shown and described two embodimerits in accordance withthe present invention, it is understood that the same is not limitedthereto but is .susceptible of numerous changes and modifications asknown to a person skilled in the art, and we therefore do not wish to belimited to the details shown and described herein but intend to coverall such changes and modifications as are obvious to one of ordinaryskill in the art.

What we claim is:

1. In a gas turbine unit for the driving of vehicles, especially motorvehicles, including a compressor and a compressor turbine mounted to adrive shaft, and a power output turbine responsive to said compressorturbine for driving a power output shaft, the improvement comprisingcoupling means for selectively coupling said compressor turbine withsaid power output shaft to controllably transfer power therebetween, andspeed reduction means provided between said compressor turbine and saidoutput shaft which is controllable for engine braking to a negativedifference and for partial-load driving to a positive difference inrotating speed relative to the speed of said output turbine, saidcoupling means including a controllable fluid coupling having onecoupling part connected to said speed reduction means between saidcompressor turbine and said output shaft and another coupling partconnected to said compressor turbine.

2. A gas turbine unit according to claim 1, wherein saidanother couplingpart of said coupling means is connected to said compressor turbinethrough a twostep controllable speed reduction mechanism.

3. A gas turbine unit according to claim 2, including partial-loadregulator means responsive to a brake instruction for controllingoperation of said coupling means and said speed reduction mechanism.

4. A gas turbine unit according to claim 3, wherein said speed reductionmechanism includes a planetary gear, braking means for braking saidplanetary gear during partial-load operation, and freewheeling meanscoupling said planetary gear to said another coupling part.

5. A gas turbine unit according to claim 4, including speed limitermeans connected to said compressor turbine for controlling the fluidsupplied to said controllable fluid couplingduring engine braking.

6. A gas turbine unit according to claim 1, including speed limitermeans connected to said compressor turbine for controlling the fluidsupplied to said controllable fluid coupling during engine braking.

7. A gas turbine unit according to claim 2, wherein said speed reductionmechanism includes a planetary gear, braking means for braking saidplanetary gear, braking means for braking said planetary gear duringpartial-load operation, and freewheeling means coupling said planetarygear to said another coupling part.

1. In a gas turbine unit for the driving of vehicles, especially motorvehicles, including a compressor and a compressor turbine mounted to adrive shaft, and a power output turbine responsive to said compressorturbine for driving a power output shaft, the improvement comprisingcoupling means for selectively coupling said compressor turbine withsaid power output shaft to controllably transfer power therebetween, andspeed reduction means provided between said compressor turbine and saidoutput shaft which is controllable for engine braking to a negativedifference and for partial-load driving to a positive difference inrotating speed relative to the speed of said output turbine, saidcoupling means including a controllable fluid coupling having onecoupling part connected to said speed reduction means between saidcompressor turbine and said output shaft and another coupling partconnected to said compressor turbine.
 2. A gas turbine unit according toclaim 1, wherein said another coupling part of said coupling means isconnected to said compressor turbine through a two-step controllablespeed reduction mechanism.
 3. A gas turbine unit according to claim 2,including partial-load regulator means responsive to a brake instructionfor controlling operation of said coupling means and said speedreduction mechanism.
 4. A gas turbine unit according to claim 3, whereinsaid speed reduction mechanism includes a planetary gear, braking meansfor braking said planetary gear during partial-load operation, andFreewheeling means coupling said planetary gear to said another couplingpart.
 5. A gas turbine unit according to claim 4, including speedlimiter means connected to said compressor turbine for controlling thefluid supplied to said controllable fluid coupling during enginebraking.
 6. A gas turbine unit according to claim 1, including speedlimiter means connected to said compressor turbine for controlling thefluid supplied to said controllable fluid coupling during enginebraking.
 7. A gas turbine unit according to claim 2, wherein said speedreduction mechanism includes a planetary gear, braking means for brakingsaid planetary gear, braking means for braking said planetary gearduring partial-load operation, and freewheeling means coupling saidplanetary gear to said another coupling part.